Cephalexin complexes with some 3d transition-metal ions

ABSTRACT

The protonation constants of cephalexin and the stability constants of its complexes with Fe [III], Cu [II], Ni [II] and Mn [II] have been determined by pH-metric titration in aqueous medium at 30 and 40 and 0.1 M ionic strength [KCI]. The metal-ligand formation constants [long beta 2] calculated, show the order as Fe [III]> Cu [II]> Ni [III]> Mn [II]. Thermodynamic parameters [delta G, delta H and delta S] calculated at 30C and 0.1 M ionic strength, show that the interaction of cephalexin and these metal ions is chelation-reaction between ionic species. Thus, the entropy change plays important role in giving the observed stability